Methylimidazolium-based ionic liquids influence the biobutanol production by solvent-producing Clostridium

Abstract

Ionic liquids (ILs) used to pretreat lignocellulosic biomass could stimulate or be detrimental to the subsequent fermentation process when the ILs retained in the biomass hydrolysate. This study aimed to investigate if the presence of the ILs including 1-allyl-3-methylimidazolium chloride ([AMIM][Cl]), 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]), 1-ethyl-3-methylimidazolium chloride ([EMIM][Cl]), 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]), and1-ethyl-3-methylimidazolium diethyl phosphate ([EMIM][DEP]) either enhanced or inhibited biobutanol production by Clostridium saccharoperbutylacetonicum N1-4. Results show that the presence of the five ILs at low concentration increased the butanol productions. The maximum butanol concentrations were obtained at 1 g L−1 for [AMIM][Cl], [BMIM][Cl], [EMIM][Cl], and [EMIM][DEP], and at 0.5 g L−1 for [EMIM][Ac]. The increase in the butanol concentrations was advantageous to the butanol and total solvent (acetone, butanol and ethanol) yields. Conversely, the butanol production rates were generally reduced by the ILs except for the observed hormesis at 0.5 and 1.0 g L−1 of both [BMIM][Cl] and [EMIM][Cl]. It was also observed that high levels of ILs impeded the speed of cell growth and thus decelerated the butanol production. Overall, the acetone-butanol-ethanol (ABE) fermentation was stimulated at low IL concentrations whereas was hindered at high concentrations.